Time-Resolved Mass Spectrometry of the Exothermic Reaction between Nanoaluminum and Metal Oxides: The Role of Oxygen Release

In this work, heterogeneous nanocomposite reactions of Al/CuO, Al/Fe 2 O 3 and Al/ZnO systems were characterized using a recently developed T-Jump/time-of-flight mass spectrometer. Flash-heating experiments with time-resolved mass spectrometry were performed at heating rates in the range of ∼10 5 K/s. We find that molecular oxygen liberated during reaction is an active ingredient in the reaction. Experiments also conducted for neat Al, CuO, Fe 2 O 3, and ZnO powders show that the oxygen are produced by decomposition of oxidizer particles. Mass spectrometric analysis indicates that metal oxide particles behave as an oxygen storage device in the thermite mixture and release oxygen very fast to initiate the reaction. A clear correlation is observed between the capability of oxygen release from oxidizing particles and the overall reactivity of the nanocomposite. The high reactivity of the Al/CuO mixture can be attributed to the strong oxygen release from CuO, while Fe 2 O 3 liberates much less oxygen and leads to moderate reactivity, and ZnO’s poor oxygen release capability caused the Al/ZnO mixture to be completely not reacting, even though the reaction is overall exothermic. It is likely that the role of the oxygen species is not only as a strong oxidizer but also an energy propagation medium that carries heat to neighboring particles.